Problem: Combine the like terms to create an equivalent expression: ${-3z-z}$
Explanation: Combine the ${z}$ terms: − 3 z − z = = ( − 3 − 1 ) z − 4 z { \begin{eqnarray} -3{z} - {z} &=& (-3 - 1){z} \\ &=& -4{z} \end{eqnarray}} The simplified expression is $-4z$.